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Municipal Wastewater Treatment – RAS


A large U.S. municipal wastewater treatment plant treats 70 MGD through two parallel 35 MGD flow trains.


The plant receives odor complaints from neighbors, characterized as “canned corn”-like, even when feeding hydrogen peroxide.

  • An engineering study identifies the return activated sludge (RAS) as the source.
  • The most offensive component is dimethyl sulfide.


975 - UNITED CARUSOL® Liquid Permanganate is injected into the Return Activated Sludge (RAS) line and the odor is eliminated.

  • There is a quick dose response when the permanganate is started.
  • There is no negative impact on the biological activity in the secondary treatment process.
  • Treatment dosage is 8 mg/L, with peak “slug” doses up to 22 mg/L.


Estimated savings are 50% of the original peroxide costs.